The Intravitreal Corticosteroid for Macular Edema (ICME) Study is a multi-center, prospective, randomized, NIH-defined Phase III clinical trial designed to assess the safety and efficacy of intravitreal injection(s) of triamcinolone acetonide in patients with macular edema secondary to diabetic retinopathy, central retinal vein occlusion (CRVO) or branch retinal vein occlusion (BRVO) who have failed to respond favorably to focal/grid photocoagulation (diabetic macular edema group and BRVO) or at least 90 days of observation (CRVO). Patients in each of these groups will be randomly assigned to one of the following: 1) conventional treatment (observation or repeat focal/grid photocoagulation for patients with macular edema associated with diabetic retinopathy or BRVO; observation for patients with macular edema associated with CRVO), or 2) treatment with intravitreal injection(s) of triamcinolone acetonide A total of 186 participants in the diabetic retinopathy group and 116 participants in each of the CRVO and BRVO groups will be enrolled at 20-25 clinical centers. Participants will be followed for 24 months, with assessments including Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity score, stereoscopic fundus photography, fluorescein angiography and optical coherence tomography performed at baseline and at 3 and/or 6 month intervals through 24 months. The primary outcome is a 10 letter or more improvement in ETDRS visual acuity assessed at 24 months. This application is to establish a Data Coordinating Center (DCC) that will provide the leadership and collaboration required to successfully implement the ICME study. As the DCC, The EMMES Corporation will be involved in all aspects of the ICME study design and management, which includes protocol development and implementation, developing data management systems, ensuring protection of human subjects, providing support to a Data and Safety Monitoring Board for study oversight, and providing statistical support for the dissemination of study results. EMMES has a broad base of experience in coordinating multi-center clinical trials and we are confident of our ability to coordinate the ICME study according to the hi hest standards of NIH-sponsored research.